diff --git a/README.md b/README.md
index f00930f5..a0de0dff 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,8 @@ The main feature of hotspot is visualizing a `perf.data` file graphically.
 
 ![hotspot FlameGraph page](screenshots/flamegraph.png?raw=true "hotspot FlameGraph page")
 
+An inlined functions has a darker border compared to a normal function.
+
 ![hotspot off-CPU analysis](screenshots/off-cpu.png?raw=true "hotspot off-CPU analysis")
 
 ![hotspot caller-callee page](screenshots/caller-callee.png?raw=true "hotspot caller-callee page")